Line follower device, especially for toys



Feb. 14, 1967 A. M. ZALKIND 3,303,507

LINE FOLLOWER DEVICE, ESPECIALLY FOR TOYS Original Filed March 13, 1958 2 Sheets-Sheet l INVENTOR.

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Feb. 14, 1967 A. M. ZALKIND 3,303,607

LINE FOLLOWER DEVICE, ESPECIALLY FOR TOYS Original Filed March 13, 1958 3 Sheets-Sheet 2 United States Patent 3,303,607 LINE FOLLOWER DEVICE, ESPECIALLY 7 Claims. (Cl. 46-244) .The application is a division of my previously filed application, Serial No. 721,128, filed March 13, 1958, now Patent No. 3,083,503. This invention relates to toys and more particularly to a device capable of following an arbitrarily drawn, erasable line.

It is an. object of the invention to provide means whereby a toy, for-example in the form of a dog, can follow a two-dimensional graphic path, which path may be obliterated or erased and a new path drawn as suits a childs fancy.

It is another object of the invention to provide a device simple and rugged in nature and economical to manufacture for simulating the motion of a toy animal, car, etc., which moves in a predetermined manner to follow an arbitrarily drawn line.

It is a further object of my invention to provide tractive means actuated by electric motors wherein gears, pulleys, belts, and even wheels are eliminated.

It is a yet further object of my invention to provide an arrangement wherein battery current is conserved.

Other objects and features of my invention will be apparent from the description to follow.

Briefly, the invention contemplates the use of electrical conductivity wherein feeler means in the form of contacts follow an insulated line placed on a metal surface, or conversely, a metallic and conductive line placed on an insulating surface.

Referring now to the drawing, FIG. 1 is an elevation of one form of the invention.

FIG. 1a is a modification of a certain portion of that form;

FIG. 2 is a front view of the device;

FIGS. 2a and b are detailed views of the motor tip shafts;

FIG. 3 is a rear view; and

FIG. 4 is a plan view showing a conductively surfaced board or plate on which the device operates and disclosing the circuit arrangement of the electrical components of the device.

FIG. 5 is a front view of another form of the invention;

FIG. 6 is an elevation partially in section of FIG. 5;

FIG. 7 is a detail elevation view of a contact brush of FIG. 5;

FIG. 8 is an elevation of one type of manually electric contact element;

FIG. 9 is a symbolic diagram showing the wiring of the invention and certain of the mechanical parts associated with the wiring;

FIG. 10 is a perspective to illustrate a metallic surface, battery box, and other elements to complete a setup for the operation of the toy vehicle;

FIG. 11 is a fragmentary perspective showing a component for effecting speed control of the vehicle.

Referring now to FIGS. 1 through 4, wherein is disclosed a preferred form of the invention, there is illustrated a device which comprises a motor mounting base or bracket means 10 having sloped sides 12, each side having fastened thereon a respective small electric motor 15a, 151). Each motor has a shaft 16 extending therefrom and engaging a supporting surface F as shown, to be hereinafter described in detail. The motors are prefheld erably of the extremely low cost and simple permanent magnet type operable by ordinary flashlight cells, such as the cells 17 which are arranged in series in what may be considered to be a conventional battery holder 20. The bracket 10 in this instance has a centrally located through-bolt 23 which extends outwardly at the front of the device and carries a leaf spring 26, the lower end of which is securely held as by nuts 28 to the through-bolt and the upper end of which is suitably fastened as by rivets 31 to the battery holder 20 to support the battery mass. A light, hollow plastic animal figure, for example that of a bloodhound 32, may be secured in any suitable manner to a bent portion 33 at the upper end of the spring. It will be understood that the dog figure substantially houses the batteries and the motors and gives the'impression of a toy animal. Thus, it will be understood that the weight of the batteries is carried flexibly by the spring 26 which may be a short strip of leaf spring material similar to that used for alarm clock springs and which is capable of flexing by virtue of the battery mass being set into vibration. A swivel block 34 is carried by throughbolt 23 and will be understood to be freely pivotal in a plane normal thereto; the swivel block 34 carrying a pair of spaced contact elements 37 which depend downwardly and rest on the surface F, being slidable thereon.

From the above description it will be apparent that the device is supported at four points; namely, on the contacts 37 and the shaft tips 16. At the forward extremity of the bolt 23 a tip-over guard 41 which may be in the form of a piece of bent wire is provided for a purpose to be hereinafter described.

The surface F is a metallic surface, for example, aluminum foil laminated to a cardboard plate P or other support means, the foil surface F thus being conductive.

Referring to FIG. 3, the plus and minus battery lugs 39 and 40 are shown and it will be seen that the negative lug 40 is connected by a wire 43 to a wire 46 which is fastened to the casings of the motors as indicated by the heavy, black dots at the ends of wire 46. It is assumed that the motors are of a type wherein the shafts and the casings are not insulated from each other and, accordingly, a current path is formed from the negative battery terminal to the tips of the shafts 16 and thus to the foil surface F. I have found that motors of this type are readily available. However, in the course of experimentation with various types of motors I have found that certain makes have their shafts insulated from the casings and, accordingly, it is necessary to provide a leaf spring contact abutting each shaft (or one shaft at least) to provide a current path to the foil from the battery terminal. For example, such a leaf spring may be provided in resilient engagement with the inner end of each or one shaft 16 'at the point 48, as seen on FIG. 3. For purpose of simplicity of construction I prefer motors wherein direct conductivity may be had through the casing to the shafts as shown.

The complete wiring diagram has been eliminated from FIG. 3 for clarity. However, by referring FIG. 4 wherein the lead 46 will be readily identified as connecting the negative of the battery to ground, it being understood that such connection is through the shaft 16, as explained above, the motor terminals (as indicated by the curlicue wires in FIG. 3) are connected so that each motor has a terminal connected to a respective contact 37 via a lead 50a, while the other terminals of the motors are connected together and to the positive of the battery, as by a lead 53. The circuit is of a very elementary nature, as will be readily appreciated from FIG. 4.

Drawn on the surface F as shown on FIG. 4 may be an arbitrarily designed path 56 in crayon, wax, enamel, paint, etc. or any other medium which serves to provide a suitable degree of insulation. In any event, the path is substantially of a two-dimensional nature and may be readily erased by any abrasive pad, such as a scouring pad of plastic or copper mesh, or steel Wool, and redrawn in any manner which suits a childs fancy. I have found masking tape or Scotch tape likewise suitable for making the path, but it is not as suitable for curvilinear configuration as ordinary crayon. Further, it is considerably more expensive and, finally, it does not have the dramatic and play value effect as a graphic line. As viewed on FIG. 3, the path 56 is shown with exaggerated thickness. However, it will be appreciated that it is substantially but a few thousandths of an inch thick and has no appreciable vertical depth which would in any way serve as a guide.

The contacts 37 straddle the path 56 being disposed on respective opposite sides thereof and spaced slightly therefrom. From the circuit diagram of FIG. 4 it will be apparent that when the device is placed on a metal surface current will run from the negative battery terminal to the surface through the motor casings and shaft tips and thence to the contacts 37 to the respective motors and, finally, from the motors to the positive terminal of the batteries. Accordingly, the motors will operate. The motors are connected so that they rotate in opposie directions as indicated by the arrows and it will be appreciated by virtue of the slanted position of the shafts that the net effect will be forward driving in an upward direction, as viewed on FIG. 4, with respect to the bottom of the drawing, and toward the reader with respect to FIG. 2, and away from the reader with respect to FIG. 3.

In order to improve traction of the shaft tips they are preferably provided with a ground flat :bevel portion, as shown in FIGS. 2a and 2b which leaves an edge 59 at the outer extremity that digs into the conductive surface and expedites locomotion. Preferably, the shaft tips should be hardened to retain permanency of the edge 59 or a hardened cap (not shown) having the general shape shown in FIGS. 2a and 2b may be slipped over the shaft tips by force fit.

From the description thus far given, the operation will be understood to be as follows:

Considering FIG. 4, both motors being energized, the device moves forward until either the left or right contact37 strikes and rides up on the insulated line 56. This breaks current continuity to the motor associated with that contact 37 and, accordingly, that motor stops rotating. However, the other contact 37 is still passing current to its respective motor which remains energized and the net effect of one motor being dead and the other motor continuing to rotate is to swing the device more or less around the shaft of the dead motor, serving as a pivot, in a direction to move the contact which had ridden up onto the line 56 off the line. The action is completely reversible. If the contact rides up on the line its associated motor is deenergized, the other motor continues to rotate, and thus steers the device in a direction so that its own contact approaches the line, but before striking it, the first contact has been removed from the line and its associated motor has become energized once more. Thus, both motors are normally energized, deenergization of either one occurring when its associated contact rides up on the line, whereupon selective deenergization effects a steering function and the device faithfully follows the line. The action is accompanied with some hunting as the contacts, in going forward, also move somewhat from side to side, depending upon the nature of the curvature of the line. At any rate, the resultant motion is to follow the path 56 in complete circuit.

I have found throughout the course of my experimentation, from a standpoint of practical toy construction and operation, that the insulated line, when drawn in a crayon color, may be anywhere from a quarter to fiveeighths of an inch wide and the contacts 37 spaced so that they are about an eighth of an inch or so from respectivesides of the line. I have further found that very effective contacts which have a minimum wax pickup are small, spherical surfaces of the order of about one-eighth of an inch in diameter and having any hard, shiny plating.

Referring to FIG. 1 it will be noted that the battery mass is set well forward with respect to the mass of the motors so that the center of gravity of the batteries is in a position with respect to the center of gravity of the motors to have a lifting effect on the motors should the batteries rock counterclockwise as viewed on FIG. 1. This counterclockwise (and return) rocking of the batteries actually occurs due to any vibration set up as the toy moves and has the following beneficial effects:

(1) When the batteries are fresh, the toy may have a tendency to overspeed (depending on weight and friction with the surface on which it operates) and in the case of such overspeeding it may shoot past the graphic line at a bend. The oscillation of the battery mass lifts the weight of the motors off the shaft tips to an extent that tractive effort is minimized or reduced to zero. Thus, the shaft tips are unloaded of weight and the toy slows down or stops dead. In other words, tractive effort is in a series of pulses, two or three or more per second, depending on the design of the device, which act as speed governors so that the toy will not have so much momentum that it will overshoot the line at a curve.

(2) The small permanent magnet motors used with such a device are very inefficient and draw surprisingly high current. The periodic unloading of the shafts permits the motors to speed up as weight is lifted off of them and the angular momentum built up in the armatures of the motors is converted into forward thrust on each return movement of the battery mass, even when the batteries are worn.

3) The entire toy is given a to and fro rocking motion which is very realistic of animal motion and highly advantageous in a toy, since it lends considerable interest in watching the operation.

The shaft tip extremities may actually leave the surface of the foil on each forward swing of the batteries, but this does not affect operation. Usually the shafts have-endwise play, so that tip engagement is maintained. If a leaf spring contact, bearing against shaft ends 48 of the motors, is used, then contact is virtually constant.

Inherent in the circuity is the fact that as either motor cuts out, there is surplus power available for the other motor (the motors being in parallel) and thus the live motor speeds up to all the more promptly serve the device to follow a curve.

It will be appreciated that the shafts will rotate with slippage in the operation of the toy, but that does not matter inasmuch as the average speed of the toy is suitable for practical purposes. The slippage of the shafts permit the toy to generate counter electromotive power so as to keep the running current down.

I have found that the swivel block 34, being rockable in a vertical plane normal to the plane of the paper as viewed on FIG. 1, or parallel to the plane of the paper as viewed on FIG. 2, is very effective in maintaining contacts 37 in intimate engagement with the running surface F, even though there maybe unevenness or irregularity in the surface. 0f course, the contacts 37 could be mounted on individual leaf springs for that purpose, but a simpler expedient is believed to be the swivel block. It should be noted that the position of the battery mass is such that a large amount of the weight of the batteries is carried by the contacts 37 to insure full contact with the surface F. Further, I have found after much experimentation that a highly satisfactory form of contact is a small, chromeplated or nickel-plated spherical surface such as is shown at the lowermost extremities of the contacts, probably of the order of one-eighth inch in spherical diameter. This form of contact has high unit stress against the surface F to maintain good electrical conductivity therebe-tween, while at the same time picks up little or no stray wax from engagement with the crayon line 56, and yet is easily slidable.

Concerning the crayon line 56, it will be appreciated that the line need not be continuous, providing the motors are reasonably synchronized. In other words, the line could be a series of short lines, although curves would preferably be continuous. However, I have found that, as a practical matter, the small permanent magnet motors used are in no way synchronized and, accordingly, a continuous line is used.

It should be further noted that lack of synchronization of the motors, which would tend to produce a curved travel of the toy under control of the faster running motor, would be compensated for by the contact which controls that motor swinging into engagement with the insulated line, thereby cutting that motor out and thus permitting the other motor to straighten out the path of travel of the toy.

While I prefer the simple sliding contacts 37, it will be appreciated that small, rolling metal wheels would be usable. However, I have found that better contact is made by the small spherical area which affords high unit stress. While I have disclosed the use of soft-surfaced aluminum foil as the running surface, the toy will operate on any suitable conductive surface, such as sheet metal, etc. Further, the slope of the shafts is not critical and any reasonable slope, which will not put to much bending strain on the shafts due to too low an angle, nor reduce the forward thrust engagement of the shaft tips with the board to a point Where there is no traction due to too high an angle, is suitable. I have found the toy operable with slopes that vary from as low as to as high as 70, but quite likely slopes outside even that large range could be used. Further analysis of the toy indicates that any type of light, plastic body could be used; for example, a bucking bronco, which might be attached at any one of several points, such as at the forward or rearward end of the through bolt 23 or at the top of the spring 26, as shown.

Also, instead of using a line made by a fully insulating medium such as crayon, a different medium might be used which would produce a line having a certain amount of resistance; for example, a mixture of wax and graphite in suitable proportion, considering the low voltage used in the device wherein the motor which engages the line does not stop completely, but is materially slowed up. Alternatively, the board surface could be of a relatively high resistive material, such as German silver, while the graphic line could be of a relatively high conductive material produceable by some types of paints and inks, or even a foil ribbon cemented to the board. Such an arrangement would likewise control the motors wherein the contacts would speed up their respective motors, upon engagement with the relatively high conductive line. In such case, the leads 50a and 50b, as shown on FIG. 4, would be crossed over to control the motors 50b and 50a respectively, so that that motor would be speeded up, which would tend to bring the device back into line following condition.

Concerning the oscillatory function of the battery mass, it will be noted that the center of gravity of the body is placed forwardly of the center of gravity of the motors, the balance being arranged so that oscillation is is readily set up by ordinary vibration produced by running of the toy. While I prefer to mount the battery mass on the flexible spring 26, which gives a regular period to the oscillations and also makes the battery mass more sensitive to vibration, while at the same time reducing the need for critical positioning of the battery mass with respect to the motor mass to produce an overbalance on forward swing of the batteries, it should be noted that the use of a spring mount is not absolutely critical. In other words, from a theoretical standpoint,

the batteries could be mounted at a very critical balancing point with a rigid mount and would still effect lifting of the motor shafts to produce the pulsing, tractive effort and the other effects. Of course, in such event, the tip-over guard, 41 or some equivalent device, would probably be required to prevent the toy from falling over on its nose, assuming the head of the toy animal did not serve such a function. Further, a less critical balancing of the battery with respect to the motors could be had by virtue of the arrangement shown in FIG. 1A wherein the batteries will be seen to be carried on a rigid bar 60 secured in a pintle 63 freely rotative in a cylindrical socket 66, and wherein the bar 60 extended upwardly and had a certain amount of free play within a slot 69 having slightly slanted sides 73 and 75. The construction could be carried in a block 78 formed as an extension of the contact carrying block, as indicated by the contact 37 connected thereto. In such case, of course, the through bolt would not extend entirely through the block 78 to the point where it would interfere with pintle 63.

Referring to FIGS. 5-11, the toy comprises slant mounted motors 300 having a common terminal connected to a sleeve 303 carried by body 305 of the toy and passing upwardly through a housing 308 which may have an ornamental button type eye 312 fastened at the front thereof. An angular metallic connector 315 is slidably and rotatively accommodated in sleeve 303 and can be inserted therein or removed therefrom. The connector 315 is at the end of a flexible lead 318 which extends over a boom 322 carried angularly over the board 325 by securement to a battery carrier base 329. Thus, it will be understood that as the toy follows a path such as 332 on the board, the connector 315 can rotate in sleeve 303 to prevent the wire lead 318 from fouling or twisting up.

The other terminals of the motors are connected to respective brushes 335 carried in a swivel block 338 suitably pivoted to the motor base which carries the motors at an angle, as shown, e.g., in FIG. 6. The brushes 335 are bunches of wire loops, as described above, suitably mounted so that a plurality of bights engage the board, and preferably, though not necessarily, bent somewhat rearwardly at their tips as shown in FIG. 7.

The motor shafts are tipped with rubber or plastic sleeves 342 which may forcibly slide towards the shaft ends as they wear. Flexible plastic sleeves get excellent traction and I have found that plastic tubing of the type molded with external ribs is fine for the purpose.

The housing 308 can be any simple plastic molding frictionally carried on sleeve 303 by means of an integral collar 345 which is slidable with reasonably tight gripping engagement on the sleeve. Polyethylene plastic would be suitable for such construction.

The battery base 329 (FIG. 10) may carry a battery housing such as 350 to the top of which may be mounted a rheostat such as 353 and it will be understood that any conventional battery holder (not shown) within the housing holds a pair of flashlight cells, as indicated at 356 in FIG. 9, one terminal of the batteries being connected to the connector 315 and the other terminal connected through the rheostat 353 to a handle 360 of insulating rod or tubing, of the order of three inches in length. A flexible lead 363 from the rheostat passes therethrough and is internally connected to a small compression spring 366, the outer end of which is abuttable with the board 325 in order to complete a circuit. Such simple arrangement, as depicted in FIG. 9, provides excellent speed control by intermittently touching the end of spring 366 to the board and a degree of control is afforded by the amount of pressure used with each tap against the board. Further, by making the diameter of the spring small relatively to the diameter of the rod 360, the handle can be laid down, as it undoubtedly will be, on the metal board without causing current to continue through the toy. In other words, the spring will be kept separated above the board by the thickness of the handle. This is of some importance in order to prevent deenergization of batteries when the toy is not actually being used, since sometimes the batteries will run solow as to drop below the cutoff voltage of the motors, but if allowed to rest for a while, they will revive. This is a well known characteristic of flashlight cells, due to polarization. However, if current is permitted to remain on, due to carelessness, in the thought that since the toy is not aunning no current is being used, the batteries will in all probability be completely ruined.

The rotative and removable connector 315 permits the toy to follow any path, and also affords a safety feature in that it can pull out of the sleeve 303 to prevent wire breakage or solder joint breakage between lead 318 and the connector 315 in the event the toy is roughly handled. Lead 318 may connect to the battery holder (not shown) in any suitable manner and preferably boom 322 is tubular so that the lead can run therethrough and emerge near the base for entry into the battery housing 350 via a slot as shown. The connections for the r-heostat 353 can be made in any obvious manner within the housing by flexible leads having sufficient slack so that the housing can be removed from the battery holder for battery replacement. The weight of base 329 and the battery housing and holder should be sufficient to keep the boom 322 in position. The boom may be merely a length of wood dowel and is preferably frictionally secured in its base socket so that it can be removed for flat packaging.

Other modes of speed control have been found to be effective. For example, instead of or in addition to the rheostat, and to enhance play value, a small piece of conductive carbon 370 (FIGS. 10 and 11) carried in a piece of insulating board 373 and exposed at both surfaces thereof so as to contact the board and be engageable with the metal tip 376 in handle 380 intermittently tapped against the piece of carbon 370 and depending on the frequency of tapping and the pressure exerted, speed control can be achieved. I have found that a carbon disc about A of an inch thick cut from the positive electrode of a standard No. 6 cell gives excellent results. Depending upon the condition of the batteries, tapping can be eliminated and variation in pressure of a tip 376 on the carbon can be used, most especially if a resilient spring tip handle, such as 360, is used against pressure response material, such as carbon or,

equivalent. However, I believe it preferable that tapping, that is, pulsing of the current, be used because the intermittent current takes less battery energy than a continuous running current and the batteries will last longer.

The tip 376 can also be used by sliding it back and forth across the carbon piece starting and ending on the insulation which surrounds the carbon. This is the equivalent of tapping. In place of a tip 376 a metal roller could be used, as shown in FIG. 8, wherein the handle 383 has a flange 386 somewhat larger in diameter than the roller 389 so that laying down of the handle on the board will prevent the roller from engaging the board and using needless battery current. Also, the flange 386 can serve as a guide against the edge 392 of the insulating member 373 for guiding the roller back and forth across the carbon base.

I claim:

1. A t-oy vehicle comprising a pair of motors having rotary motor shafts extending downwardly therefrom with said shafts mounted at an acute angle with relation to the vertical axis of said vehicle and said shafts serving as means to support at least a portion of said vehicle on a surface and effect propulsion of said vehicle by direct rotary engagement of said shafts with said surface.

2. A toy vehicle as set forth in claim 1, said portions of said shafts having means to enhance driving engagement with said surface.

3. A toy vehicle as set forth in claim 1, including a movable mass carried by said vehicle and mounted for movement between two positions With respect to said shafts so as to intermittently reduce weight loading on said shafts during operation of said vehicle, and means for effecting periodic movement of said mass.

4. A toy vehicle as set forth in claim 3, said motors being electrically energized and said mass comprising battery means for energizing said motors.

-5. A toy vehicle as set forth in claim 3, and a flexible mount for said mass capable of being oscillated .by vibration upon movement of said vehicle.

6. A toy vehicle as set forth in claim 1, said motors being electrically energizable and said vehicle having a pair of contacts slidable on said surface and coacting wit-h said shafts to support said vehicle.

7. A toy vehicle as set forth in claim 6, said contacts being comprised, in each instance, of a plurality of flexible wire loops having looped portions for slidable engagement on said surface.

References Cited by the Examiner UNITED STATES PATENTS 2,054,644 9/1936 Wulfert 46243 2,488,464 11/ 1949 Arpin 46244 2,537,281 1/1951 Roshak.

2,650,337 8/1953 Raver 318-305 2,667,613 1/ 1954 Tra'vitt 318305 2,735,683 2/ 1956 Klein et al. 274-39 X 2,768,697 10/1956 Shotwell 46244 X 3,038,275 6/1962 Curci 46247 3,083,503 4/ 1963 Zalkind 46--244 3,086,319 4/ 1963 Frisbie et al. 46244 3,124,902 3/1964 Gowland et al. 46243 RICHARD C. PINKHAM, Primary Examiner. L. J. BOVASSO, Assistant Examiner, 

1. A TOY VEHICLE COMPRISING A PAIR OF MOTORS HAVING ROTARY MOTOR SHAFTS EXTENDING DOWNWARDLY THEREFROM WITH SAID SHAFTS MOUNTED AT AN ACUTE ANGLE WITH RELATION TO THE VERTICAL AXIS OF SAID VEHICLE AND SAID SHAFTS SERVING AS MEANS TO SUPPORT AT LEAST A PORTION OF SAID VEHICLE ON A SURFACE AND EFFECT PROPULSION OF SAID VEHICLE BY DIRECT ROTARY ENGAGEMENT OF SAID SHAFTS WITH SAID SURFACE. 